It is often necessary to isolate a precision transducer from external stress. Such stress may be caused by mechanical distortion of the case (or other support structure) to which the transducer is mounted, or by differential thermal expansion or contraction between the transducer and the case. Isolation from external stress can in principle be achieved by using a compliant mounting system. However, a compliant mounting system will not in general provide precise and stable alignment of the transducer with respect to its case. For many transducers, (e.g., accelerometers), such alignment is critical for achieving proper operation. A compliant mounting system may also result in unwanted mechanical oscillation of the transducer when the case is exposed to vibration.
One prior accelerometer mounting technique has been to connect the accelerometer to the case by means of a metal ring, or by means of a structural adhesive such as an epoxy resin. The prior noncompliant mounting techniques result in stress being transmitted to the accelerometer due to differential thermal expansion between the accelerometer and the mounting ring and case. These prior techniques also transmit stress to the accelerometer when the case is subjected to mechanical distortion. Distortion of the case be induced by mounting the case to an external structure, or by differential thermal expansion between the case and the external structure. Such stress may lead to thermally induced errors in the accelerometer output.
A second type of prior accelerometer mounting system is described in PCT patent application No. WO 88/00348. This system utilizes a device comprising a plurality of mounting elements joined by bridge sections to form a ring from which the mounting elements extend in an axial direction. In a first embodiment, the mounting elements include ends that are connected to the case, while the ring itself is directly joined to the transducer. Although this technique provides a stable mount with a certain degree of relief from thermal strain, the direct mounting of the ring to the transducer nevertheless produces thermally induced strains whenever the mounting device and transducer are fabricated from materials having different thermal expansion properties. In a second embodiment, the mounting elements are divided into two interleaved sets, with one set being connected to the transducer, and the other to the case. While this approach avoids the direct bonding of the ring to the transducer, it effectively divides the number of support points by two, therefore, providing a less rigid mount.